That`s an interesting thought.
So on that basis, if microsoft ship 17 million copies of XP, they can be classed as 17 million sold copies of XP. Which is what seems to be going on. The matter that companies have 100s of XP packages each in their cupboards not going to be used, doesn`t reflect on the figures. (I`ve already cleared out cupboard of 95, 98se and ME - so I can see the storage issue, kept 1 of each for legacy app reasons believe it or not)
Also if they ship a product that the consumer never buys, it can also be recorded as a record sale if the shipment is big enough.
If Sony ship 40 million units of the PS4 on day 1 to retailers, it becomes a 40 million unit sale on that day. The larger the shipment, the bigger the claim of the biggest selling console on day 1. Doesn`t matter if the consumers are out purchasing the new Nintendo Widdle - that only shipped 20 million units to retailers.